Healing: Non Union; what is it? what causes it? can it be treated? what can we do?

Nonunion is failure of the healing process to go to completion. You will recall that normal healing takes place in stages - bleeding - blood clot - invasion by blood vesssels growing in - scar formation - bone mineral laid down in the scar to transform it into bone. In most nonunions the process gets hung up at the scar formation stage. Ossification (deposition of bone mineral) may happen in some of the scar but not all of it so the bond between the fracture fragments remains pliable scar not rigid bone.

The cause in most nonunions is impossible to determine. Even though I am going to discuss events that do increase the risk of nonunion it happens most often even when everything is done right and there are no warning signs.

There are two common predisposing features - movement of the fracture fragments and poor blood supply.

Movement. If the fracture fragments are poorly immobilized the scar between the fragments (soft callus) may be attenuated. Bone mineral forms more easily in tissue which isn't being stretched and pulled. This is the reason that most orthopaedic treatment of fractures involves using internal fixation or casts to keep the fracture still. It is also the reason that OS try to keep people from walking on their fracture too early. If hard callus hasn't formed yet the risk of nonunion from premature stress on the fracture sight is too important to be ignored. It is not an absolute rule and dinosaur bones were healing over 100 million years ago without benefit of OS or fracture treatment. However, to give your fracture every chance to heal grit your teeth and follow instructions!
Sometimes the surgeon's intention to immobilize the fracture fragments isn't or cannot be realized. A fracture that has been operated on but is still mobile is (IMO) at increased risk for nonunion because the surgery also compromises the blood suppply.

Bone develops in tissue with a good blood supply. It needs energy and oxygen to manufacture bone mineral. Parts of the body like the neck of the femur, the talus and the lower third of the tibia have a blood supply which is easily knocked out by the injury. These areas have a higher incidence of nonunion.

Some surgical techniques interfere with blood supply. Putting a plate on a fracture often involves stripping the lining of the bone away. The blood supply of the outer third of the bone comes from this lining so the blood suppply hass to be re-established for the bone to heal. Fortunately this does usually happen. OS are trying to develop less invasive techniques of fixing fractures but the problem is that to see the bone to reduce the fracture we have to clear away the soft tissue; and the soft tissue is where the blood supply gets to the bone.

To sum up, a recipe for non-union would be an injury to a vulnerable area which damages the blood supply, treated by open surgery which doesn't manage to stabilize the fracture and the patient starts walking too early! Together these factors would create a serious risk of nonunion.

The treatment of nonunion is to reverse the conditions which may predispose; freshen up the area to allow a new bllod supply to grow in, immobilise the fracture, and use bone graft to give the process of ossification a good start. Most often this means surgery with bone grafting and exchange of hardware or the Ilizarov method being popular surgical choices. There are two unproven methods which may offer big advances in future - genetic engineering to "turn on" the healing process and bone growth stimulation by electrical stimulation or ultrasound.

The only thing a patient can do is avoid putting premature stress on the fracture. There is a lot of anxiety waiting for the OS to give the go ahead on cast removal and return to weight bearing. What the OS is worried about is whether the fracture has healed enough, has laid down enough bone, to be stimulated by the stress of walking and increased activity or whether it is still too early and putting weight on it will predispose to nonunion. All OS have made this judgement and I venture to say that all OS have got it wrong more than once.

Myles Clough MD

I will try to assemble some links to support this summary of a complex subjectFrom: Elle'

I have read a few posts regarding Non Union and thought
this might be a good addition as I see you cover bone grafts.

What causes Non Union ?
How can it be treated ?
Is there anything the patient can do?

10/13/00 I was hurt, femor broke in 3 places, internal fixation done with longest plate they say is made. Was non wieght bearing for 6 months, started PT got to cane stage in 3 mo. Pain was always awful, xrays showed bone grownth. Then on 10th. month after 1st break it broke again and the hardware snapped. They re did the surgery I am now at the 6 month stage and began therapy again. It hurts, should this be making me this miserable. I have only been to PT this time 4 visits in the pool. It takes two days to recovery from it and it is PT time again. Is this normal.

Myles
I have a distal fibula fracture, not a 'bad' one. When my second fibreglass cast was put on after 6 days, I was told I could start weight bearing, slowly. There is just no way. I get pain when I just put the foot down to steady myself, without weight. I worry that this is too soon and wouldn't even consider doing this for at least another 2 weeks or when I feel my ankle 'tells' me it's OK. Do you think 6 days is too early? Regards Jean